The invention relates to a process for the preparation of a hydrocarbon mixture from a mixture of carbon monoxide and hydrogen with an H.sub.2 /CO molar ratio of less than 1.0, using a trifunctional catalyst combination containing one or more metal components with catalytic activity for the conversion of an H.sub.2 /CO mixture into acyclic hydrocarbons and/or acyclic oxygen-containing hydrocarbons, one or more metal components with catalytic activity for the conversion of an H.sub.2 O/CO mixture into an H.sub.2 /CO.sub.2 mixture and a crystalline silicate having the capability of catalyzing the conversion of acyclic hydrocarbons and acyclic oxygen-containing hydrocarbons into aromatic hydrocarbons. The said crystalline silicates are characterized in that they have the following properties:
(a) thermally stable up to a temperature about 600.degree. C.,
(b) an X-ray powder diffraction pattern showing, inter alia, the reflections given in Table A.
TABLE A ______________________________________ Radiation: Cu - K.alpha. Wavelength 0.15418 nm 2 .theta. relative intensity ______________________________________ 7.8-8.2 S 8.7-9.1 M 11.8-12.1 W 12.4-12.7 W 14.6-14.9 W 15.4-15.7 W 15.8-16.1 W 17.6-17.9 W 19.2-19.5 W 20.2-20.6 W 20.7-21.1 W 23.1-23.4 VS 23.8-24.1 VS 24.2-24.8 S 29.7-30.1 M ______________________________________
wherein the letters used have the following meanings: VS=very strong; S=strong; M=moderate; W=weak; .theta.=angle according to Bragg.
(c) in the formula which represents the composition of the silicate, expressed in moles of the oxides, and in which, in addition to oxides of hydrogen, alkali metal and/or alkaline-earth metal and silicon, there is present one or more oxides of a trivalent metal A selected from the group formed by aluminum, iron, gallium, rhodium, chromium and scandium, the A.sub.2 O.sub.3 /SiO.sub.2 molar ratio (for the sake of brevity further designated m in this patent application) is less than 0.1. In an investigation by the Applicant concerning this process it was found that it has two drawbacks. In the first place, when using space velocities acceptable in actual practice, the conversion of the H.sub.2 /CO mixture is found to be unsatisfactory. Further, the process yields a product substantially consisting of hydrocarbons with at most 12 carbon atoms in the molecule and only very few hydrocarbons with more than 12 carbon atoms in the molecule.
Further investigation by the Applicant concerning this process has shown that the two above-mentioned drawbacks can be obviated by giving the reaction product, or at least its C.sub.2.sup.- fraction, an after-treatment by contacting it with a catalyst containing one or more metal components with catalytic activity for the conversion of an H.sub.2 /CO mixture into acyclic hydrocarbons, which metal components have been selected from the group formed by Ni, Co and Ru, on the understanding that if the feed for the second step has an H.sub.2 /CO molar ratio of less than 1.5, water is added to this feed and that in the second step a bifunctional catalyst combination is used, which contains, in addition to metal components with catalytic activity for the conversion of an H.sub.2 /CO mixture into acyclic hydrocarbons, also one or more metal components with catalytic activity for the conversion of an H.sub.2 O/CO mixture into an H.sub.2 /CO.sub.2 mixture. In this way it is achieved that, when using space velocities acceptable in actual practice, not only a very high conversion of the H.sub.2 /CO mixture is obtained, but also that the reaction product consists substantially of hydrocarbons with more than 12 carbon atoms in the molecule.